Pressure-flow studies in man: effect of atrial systole on left ventricular function

Abstract

A B S T R A C T In order to evaluate the effects of atrial contraction on left ventricular function, the pressure gradient technique was used to measure instantaneous aortic blood flow and pressure in nine patients, six having complete heart block and three having normal sinus rhythm. From these data both left ventricular stroke volume and stroke work were calculated. Ventricular rate was controlled by transvenous right ventricular pacing over a range of 50-158 beats/min. At each heart rate, beats which were not preceded by a P wave served as controls. The other beats were divided into six groups according to the duration of the preceding PR interval. The results indicated that stroke volume and stroke work were always affected similarly. In one patient the presence of a P wave did not alter the subsequent stroke volume significantly. In the other patients, beats preceded by P waves had stroke volumes greater than the controls. In general, there was no difference in stroke volume for beats preceded by a P wave having a PR interval within the range of 0.05-0.20 sec. As the PR interval lengthened beyond 0.20 sec stroke volume tended to decrease, especially at more rapid heart rates. The absolute increase in stroke volume after a beat preceded by a P wave (PR interval 0.05-0.20 sec) was quite variable among the patients. For a given patient the absolute increase in stroke volume was essentially independent of heart rate. The percentage change in stroke volume, however, was always greater as the heart rate increased.

From Mouse to Whale

“…The atrial systole is an important determinant of ventricular performance. 38 It has been demonstrated in humans and dogs 35,39,40 that there is a wide range of timings that allows atria and ventricles to work sequentially. However, there is also an optimal PR interval that is associated with the best ventricular hemodynamic efficiency.…”

Study on site of acute myocardial infarction associated with arrhythmias and outcome

“…13 Incidence of malignant ventricular arrhythmia associated with infarction are changed by the extent of the underlying infarction. 14 Inferior wall myocardial infarction report for 40-50% of all acute myocardial infarction with mortality rates of 2-9%. 15 Bradyarrhythmias occur more frequently in inferior than anterior wall myocardial infarction.…”

Pressure-flow studies in man: effect of atrial systole on ventricular function in mitral stenosis

“…Mitchell, Gupta, and Payne's work in the dog (12) and reports from this laboratory (8) in patients without mitral valve disease show the absolute increase in stroke volume created by effective atrial systole to be independent of heart rate. In the patient with mild mitral stenosis, we found similar results.…”

“…There is a variation among the normals but all exceed the changes seen in those with mitral stenosis. DISCUSSION The importance of atrial contribution to left ventricular function in the experimental animal (9, 10) and in normal humans (8) has been thoroughly evaluated, but little has been written about its significance in rheumatic heart disease and, in particular, pure mitral stenosis. Carleton and Graettinger, using synchronous and sequential atrial pacing, reported effective atrial systole to improve normal human's left ventricular output by 20% but found no effect on individuals with mitral stenosis (1).…”